The DRC wines are not immune to the usual problems that wines can have.
I once had a badly corked bottle of their Echezeaux from the 70s - I do
not recall the exact year. Since many people age their wines for many
years, returning the corked bottle to the wine shop often is not an
option.

Michael Broadbent has tasted the 66 La Tache several times, with a last
tasting in 1997. He rated the wine at best 5-star. He notes a bottle or
two not quite as good as this. From his notes, this wine was fairly
tannic in youth. It sounds as if your bad bottle was far worse than
anything Broadbent tasted.

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